1. Field of the Invention
The present invention relates to an optical filter module for wavelength multiplexing and demultiplexing and a method of manufacturing the same, and more particularly, to an optical filter module for wavelength multiplexing and demultiplexing in the form of an arrayed waveguide grating which is used in an optical communication system using a wavelength division multiplexing method, and a method of manufacturing the same.
2. Description of the Related Art
FIG. 1 is a diagram illustrating an example of a conventional optical filter module for wavelength multiplexing and demultiplexing in the form of an arrayed waveguide grating.
Referring to FIG. 1, signal lights which are wavelength-multiplexed through an input waveguide 101 are optically coupled with an input-stage star coupler 102 in the form of a slab waveguide. Then, the signal lights further propagate and are then coupled with array waveguides 103.
Individual waveguides forming the array-waveguide 103 are sequentially arranged so that the optical path of each waveguide has a predetermined length different from that of the other waveguides. Signal lights propagating through respective individual waveguides are optically coupled with an output-stage star coupler 104 in the form of a slab waveguide. Then, the signal lights further propagate and are then optically coupled with output waveguides 105.
Through a series of these processes, the wavelength-multiplexed signal lights input through the input waveguide 101 are separated in terms of wavelengths and output through respective output waveguides 105.
When the signal lights, each of which has a wavelength corresponding to one of the output waveguides 105, are input to the output waveguides 105, the wavelength-multiplexed signal lights are output in a collected form through the input waveguide 101. Accordingly, when the signal lights are input to the output waveguides 105, the optical filter module performs a wavelength-multiplexing function.
In order to achieve a good performance of the optical filter module, it is necessary to minimize the loss of optical power of the signal light which is accumulated in a plurality of continuous optical coupling and propagation processes, as described above, and the phase error of the signal light which is accumulated when the signal process propagates through the array-waveguide 103. Thus, an optical filter module that minimizes the loss of optical power of signal light and a phase error of the signal light, is required.